Studies On Interactions At Interfaces Of Phosphorothioate Oligo-DNA And Nanocrystals

Most important biomolecules, such as DNA, protein etc, their size are 2 to 200 nm similar to nanoparticles. Beacause of the special structure and fundamental features, biomolecules display the several surface and interface properties. Biomolecules are important future building blocks for the formation of nanoparticle architectures of predesigned shapes, sizes and compositions. Nanoparticle have highly interesting optical, electronic, and magnetic properties due to quantum confine effects and surface effects. The using of nanoparticles as biotechnological tool are particularly attractive. one of such application is using fluorescent semiconductor as labels for biological tagging experiments. DNA, as one of most important biomolecules, is particularly suitable to serve as a construction material in nanosciences. The most-studied of the antisense oligodeoxynucleotides are the phosphorothioate analogs (PS oligo-DNA), and there have been many reports in which PS oligo-DNA were used to inhibit over-expression of cellular gene product implicated in cancer and inflammation, HIV-1 replication in HIV-1 infected cells and viral replication. For PS oligo-DNA, the sulfur atom introduced on the phosphate backbone dominates the interaction between the DNA and the nanocrystal. My dissertation is focused on studying the interactions at interfaces of the PS oligo-DNA and nanocrystal. It is attempted to supply a new way to nano-assembly by PS oligo-DNA. There are mainly there parts in this dissertations: 1) The coordination sites of phosphorothioate oligoG10 (PS-oligoG10) with Cd2+ and CdS nanocrystal are studied. It is found that after coordinated with phosphate group of the DNA, Cd2+ ions can destroy the guanine-guanine hydrogen bond of quardruplex assembly of PS-oligoG10 and induce the bending of PS-oligoG10 through coordination of Cd2+ with its phosphate groups. The bended PS-oligoG10/Cd2+ complex is observed as nanosphere with diameter of about 2 nm as shown by TEM. After addition of sodium sulfide, TEM image shows CdS nanocrystals with diameter of about 5 nm was obtained. As a result, the coordination between Cd2+ and PO2-group of the DNA is cleaved and the coordination site of the DNA with CdS nanocrystal is identified to transfer to guanine residue of the DNA. 2) Protein-sized surface Cd2+-rich, S2--rich and neutral CdS nanocrystals were employed as "inorganic proteins"to study the interface binding of...